1. Department of Clinical Medicine; University of Bergen; Bergen Norway
2. Section of Gastroenterology; Department of Medicine; Haukeland University Hospital; Bergen Norway
3. National Centre of Functional Gastrointestinal Disorders; Haukeland University Hospital; Bergen Norway
4. Unger-Vetlesen's Institute; Lovisenberg Diaconal Hospital; Oslo Norway
5. Department of Clinical Science; University of Bergen; Bergen Norway